ci: bump actions/upload-pages-artifact from 3 to 4 in the actions group

Bumps the actions group with 1 update: [actions/upload-pages-artifact](https://github.com/actions/upload-pages-artifact).


Updates `actions/upload-pages-artifact` from 3 to 4
- [Release notes](https://github.com/actions/upload-pages-artifact/releases)
- [Commits](actions/upload-pages-artifact@v3...v4)

---
updated-dependencies:
- dependency-name: actions/upload-pages-artifact
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/docs.yml

@@ -39,7 +39,7 @@ jobs:
       - name: Build docs
         run: sphinx-build -M html docs docs/_build
       - name: Upload docs artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@v4
         with:
           path: docs/_build/html
       - name: Deploy to GitHub Pages